Piston expander for slotted and unslotted piston skirts



June 8, 1948. WOREL 2,442,834

PISTON EXPANDER FOR SLOTTED AND UNSLOTTED PISTON SKIRTS Filed Sept. 13, 1940 IA/ vnv'rom mm d. woma. pr ///.5 firm/W575.

Patented June 8, 1948 PISTON EXPANDEB FOB SLOTTED AND UNSLOTTED PISTON SKIRTS Glen J. Wore], Minneapolis, Minn.,

Thexton Manufacturing Company.

assignor to Minneapolis, Minn, a corporation of Minnesota Application September 13, 1940, Serial No. 356,608 3 Claims. (01. 309-12) This invention relates to expanders for the skirts of pistons of internal combustion engines and the like, and particularly to an expander which is applicable and effective upon a piston skirt which is unslotted as well as to pistons having longitudinal and transverse slots formed in the skirts thereof.

When the cylinders of internal combustion engines and similar devices become worn they develop an out-of-round shape and the skirts of the pistons working in the cylinders tend to slap against the worn cylinder walls causing the well known piston slap and a resultant tilting of the piston which will quickly wear the edges of the oil rings on the piston so that oil will pump past the rings and the eiiiciency of the engine will drop considerably.

One of the objectsof my invention is to provide an improved and extremely simple expander which resiliently exerts an expansive action on portions of the piston skirt intermediate of the bosses and in a direction transverse to the axis of the wrist pin, thereby resiliently taking up for normal wear and eliminating the necessity for reboring the cylinder.

A further and more specific object is the provision of a preferably integral, curved leaf spring member of some considerable width interposed between the wrist pin bosses and inner wall of the skirt, and exerting outward pressure on a portion of said inner wall and particularly applicable to pistons which do not have slotted skirts and pistons which have only tongue-like portions slotted out from the skirt thereof, such as are used in the automobiles manufactured by the Chrysler Corporation.

A further object is the provision in. such a piston expander of means for positively engaging a spreading tool to expand the expander longitudinally for facilitating insertion thereof in operative position in a piston.

Another object is the provision of means engaging the wrist pin bosses which will afford maximum contact area and greatly lengthen the effective life of the expander without variance in the degree of expansive force exerted.

Still another object is to provide a highly eflective, cheap piston skirt expander having a high expansive force to produce a substantially oval shape in the piston skirt so that the piston will more closely fit worn cylinders with the result that the piston will be guided more accurately and piston slap will be eliminated.

These and other objects and advantages of the invention will be more fully set forth in the fol- 2 lowing description made in connection with the accompanying drawings wherein like reference characters refer to the same parts throughout the several views, and, in which:

Fig. 1 is a bottom plan view of a piston of the unslotted skirt type such as is used in the present model automobiles built by the Ford Motor Company, of Detroit, Michigan, with an embodiment of my invention applied thereto, the dotted lines indicating the removing and insertion tool;

Fig, 2 is a vertical section taken through approximately the wrist pin bosses;

Fig. 3 is a section of the embodiment of my expander shown in Figs. 1 and 2 detached,said section being taken on the line 3-3 of Fig. l; and

Fig. 4 is a front elevation of a somewhat modified form of the invention adapted for application to piston skirts having an internal, circumferential rib disposed a short distance above the lower edge of the piston skirt.

Injigs. 1 and 2, a piston of the unslottedskirt type is shown, having the usual domed head 5, the cylindrical periphery of which is provided with the usual piston ring grooves 5a and lands 5b. The head is constructed of greater thickness than the depending piston skirt 6 which is continuous with the head, being outwardly and circumferentially oiiset from the inner periphery of the head a short distance, as shown. The skirt 6 in this type of piston is continuous, comparatively resilient and flexible, and is not provided either with circumferential, horizontal slots or longitudinal slots, as is common in many types of pistons.

The usual opposed wrist pin bosses I of relatively heavy construction are integrally formed or otherwise rigidly secured to the inner walls of skirt 6 and, of course, are topped and ground to act as bearings for the wrist pin.

My improved piston skirt expander, shown in Figs. 1 to 3, inclusive, comprises a relatively wide leaf spring member curved in the general form of a U, and having the legs 8 of the U diverging from the central or expansion application portion 9 thereof, which is of somewhat concavoconvex shape, the concave surface being disposed outwardly. This expansion application,

' portion 9 is preferably the widest part of my expander, the legs 8 diverging gradually from central portion 9 to the leg extremities 8a. The leg extremities 8a are out-turned and curved to nicely fit the external periphery of the tapered wrist pin bosses I, as shown in Fig. 1, and they are further shaped concavely in a transverse direction to conform to the circumferential shape of bosses 1, thereby properly centering th'e expander in operative position and engaging or pertially surrounding the opposing homes. Not only is the expander-properly held in position in this manner but the leg extremities 811. as best shown in Fig. 1. permit said extremities to move along the bosses I as the parts expand and contract due to different heat conditions.

In operative position my expander is applied, as shown in Figs. 1 and 2, interposed between the bosses I and the inner wall of the piston intermediate of said bosses and applying pressure through a relatively large area on the expansion application portion 9 of the leaf spring member. The pressure so applied resiliently expands the intermediate portion of the skirt between bosses 1, enlarging the diameter of the piston taken transversely of the axis of the wrist pin bosses to take up for wear and prevent piston slap in used pistons and cylinders.

It should be further noted that this expansion is in a direction in line with the elongated cross sectional portion of the worn cylinder so that the piston is adapted to the out-of-round shape of said cylinder. My expander may be applied to unslotted pistons or may equally well be applied to pistons havingcircumferential slots with connected vertical slots forming rectangular tongues or portions which may be resiliently sprung out, such as are used in the present type of engines manufactured by Chrysler Corporation.

I prefer to construct the U-shape leaf spring member, as shown in Figs. 2 and 3, with the lower edges of the legs and expansion application portions diverging less than those of the upper portions, thereby leaving a lesser amount of expansion application surface below the longitudinal center line of the expander than above. The reason for this is that in most pistons, due to the relatively heavy and rigid head, more application of pressure is needed adjacent the'head on the skirt than adjacent the lower edge thereof to produce a uniform expansion through the entire height of the skirt.

It is to be understood, however, that I am not limited to such a structure.

It will be noted that the over-all length of my expander from leg extremity to leg extremity is less than the are drawn between the points where the opposing bosses emerge from the inner wall of the skirt. Consequently, by spreading or expanding the leaf spring member longitudinally and thereby decreasing the working width thereof, I am able to veryeasily and quickly slip my expander into a piston. A tool is provided for effecting such longitudinal expansion and an important point of my invention is the provision of positive tool engagement means incorporated in the expander, whereby this longitudinal stretching or expansion maybe effected. To this end I provide a tool-receiving aperture H) in each of the legs 8 adjacent the out-turned extremities thereof. A pair of pliers P having laterally and outwardly projecting studs II at the ends and outer sides of the working jaws thereof are preferably provided for stretching, applying and removing my expanders. The studs l I fit the apertures l and when the pliers are spread produce the longitudinal expansion and cause the expander to be narrowed in width for ready insertionand interposition between the bosses 1 and intermediate wall of the piston skirt. In applying the expander the out-turned and transversely concave extremities is readily seat and center 4 themselves upon the bosses I, assuring the correct working position of my device.

In Fig. 4 I have shown a slightly modified form of expander adapted for application to pistons of the type having an internal, circumferential rib disposed a short distance above the lower edge of the piston skirt. Here the expansion application portion 9 of the expander is provided with a horizontal, elongated recess or slot ll of a width to accommodate and receive a portion of the rib so that the pressure from the surface of portion 9' may be directly applied to the skirt itself. rather than to the rib. By providing a cut-out portion such as the slot is it will lie over the rib and against the main wall of the piston and at the same time permit flexing of the expander at its central portion.

From the foregoing description it will be seen that I have provided an extremely simple, highly eflicient and comparatively inexpensive expander adapted for application to practically all types of internal combustion engines as-well as many types of compressors and other motors. and capable of being used with high success on unslotted piston skirts and skirts having tongue portions slotted therefrom.

It will, of course, be understood that various changes may be made in the form. details, arrangement and proportions of the parts without departing from the scope of my invention.

What is claimed is:

1. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed cylindrical wrist pin bosses having longitudinally smooth outer surfaces and an annular depending skirt of resilient, somewhat flexible material, of an expander comprising, a spring member having a medial curved flexing portion I area, said legs terminating in retaining feet having concave sliding surfaces slidably and closely fitting the circumferential contour of said bosses. and said legs and feet being spaced to normally position said feet at positions intermediately of said bosses with freedom for limited sliding movement of said feet longitudinally of said bosses in both directions as said curved portion is flexed.

2. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed cylindrical wrist pin bosses that are smooth and unbroken from end to end on their longitudinal side surfaces, and an annular depending skirt of resilient somewhat flexible material, of an expander comprising, a spring member having a medial curved flexing portion having an outwardly extending pressure-applying area and having relatively inflexible legs extending substantially straight inwardly from said pressure applying area. said legs terminating in smooth-bottomed feet that slidably engage and ride upon said bosses, said feet being spaced to normally contact only the intermediate portions of said bosses and having capacity for free sliding movement longitudinally of the bosses.

3. A piston. expander for a conventional type of internal combustion engine piston having the usual opposed cylindrical wrist pin bosses and the usual annular depending skirt of resilient. somewhat flexible material comprising a spring member having a medial curved flexing portion including an outwardly extending pressure applying area adapted to be disposed against theresilient skirt of a piston and having relatively in- REFERENCES CITED The following reierenees are of record in the file of this patent:

6 UNITED STATES PATENTS Number Number Name Date Grant Oct], 1932 Moore May 81, 1988 Keaton Aug. 23, 1988 Brenner July 11, 1939 Butler Oct. 10, 1939 Dillow Dec. 26, 1939 FOREIGN PATENTS Country Date France i. Apr. 6, 193'! 

